Spark plug



April 15, 1930. E. 1. JOHNSON SPARK PLUG,

me@ web. 11, 1927 IWW/mm1 EEA-VL L T. T 'h1-1512111.

a wlw/ y w Patented Apr. 15, 1930 UNITED STATES EARL J. JOHNSON, OF SILVERBOW, MONTANA SPARK PLUG Application filed February 11, 1927. Serial No. 167,556.

The present invention relates to improvements in spark plugs, and the primary object of the invention is to provide an improved spark plug embodying features 3 5 whereby the central electrode of the plug is readily removable from the body portion of the plug for the purpose of cleaning the electrode.

A further obj ect of the invention is to provide a spark plug having a removable central electrode which may be readily removed for the purpose of cleaning or heating of the electrode without removal of the body portion 'of the plug Jfrom its threaded connection 515 with the engine.

, A further object of the invention resides Vin the provision of a spark plug embodying va removable electrode which when removed from the body portion of the plug provides an opening or way through the plug whereby the engine may be primed by introducing gasoline or analogous fuels through the way for the electrode.

A further object of the invention resides in the provision of a spark plug having a removable central electrode so detachably connected at its outer end to the outer end of the plug, as to insure the forming of an air tight and leak proof joint between the removable electrode and the body portion of the plug when the electrode is in position within the plug body portion.

A still further and important object of the invention resides in the provision of a spark V plug as set forth, embodying relatively few and simple parts, and one wherein the parts are readily replaceable.

Other objects and advantages of the invention will be apparent during the course of the following detailed description, taken in connection with the accompanying drawing forming a part of this specification and in which drawing:

Figure 1 is a view illustrating the various parts of the plug in disassembled relation.

Figure 2 is a central longitudinal section through the plug and showing the parts in' assembled operative relation. Figure 3 is a view part in side elevation and part in longitudinal section, and showing the manner in which the central elec'- trode is moved into leak proof engagement with the shoulder provided in the insulating core.

Figure et is a transverse section on line us 4-4 of Figure 3 and looking in the direc tion of the arrows.

Figure 5 is a transverse section on line 5-5 of Figure 2.

Figure 6 is a view illustrating the manner in which the central electrode may be cleaned by holding the firing point thereof over a ame for removal of the oil and carbon deposits from the firing point of the electrode.

In the drawing, and wherein similar ref- @1i erence characters designate corresponding parts throughout the several views, 10 designates a metal shell of the usual construction, embodying the wrench engaging portion l1, and the reduced threaded portion 12 which is il intended for threaded engagement within a threaded opening of the engine block. The shell 10 is provided at its inner end withthe usual electrode 13 which is grounded through the shell to the engine. The shell is provided with the usual internal seat 14; against which the packing washer 15 seats, and threaded into the upper end of the wrench portion l1, is the usual packing gland or nut 16.

This shell 10 and packing nut 16 are of SO usual and well known construction, and in the present invention, serve to support the porcelain or insulating core 18, and which insulating core is provided with an enlarged portion 19 which is intended to be moved by means of the packing nut 16 into sealing engagement with the washer 15. This insulating core 18 is provided with an axially disposed way or port 2O which extends from the inner to the outer ends of the core, and 50' the way is reduced in diameter at its inner end as at 21, for providing an annular shoulder or seat 22 adjacent the inner end of the core. The extreme outer end of the way 20 is enlarged as at 23, and opening into the env larged portion 23, at diametrically opposite points, are key ways 24 which open at the` outer end of the core 18 and preferably converge toward their inner ends as illustrated in Figure 2. Provided adjacent the outer end 15?) of the core 18, is an annularly extending groove 25, and the object of this groove will be subsequently set forth. As in usual construction, upon removal of the packing nut 16, the insulating core 18 may be readily Withdrawn from the metal shell 10.

Mounted for detachable connection with the core 18, is -a centra-l electrode 30 embodying a stem portion 31 of cylindrical formation for slidably and rotatably fitting Within the bore 20. The inner .end of the stem 31 is reduced in diameter as at 32 for forming a firing point, and Which reduced portion provides an annular shoulder 33 which When the stem is properly inserted in the Way 20, is intended to engage the annular seat 22 provided adjacent the inner end of the Way. Carried' by the outer end of the stem portion 31, and Which stem portion may be formed of Monel or any other suitable metal is a metallic head 35 which may be connected with threaded connection With the reduced screw threaded terminal portion 37 of the stem. The head 35 is preferably provided at its vinner end with knurled portions 38y providing an annular groove 39, and the outer end of the head is preferably of spherical formation and provided With a transverse slot 40.4 The annular groove 39 and, spherical.

outer end of the head 35A provide means for receiving diierent types of conductor terminalswhich are to be electrically connected.

portion 42 providedA With diametrically dis-- posed keysv43 Which, are ini'iendedy to engage in the keyways24 With thel outer ends of 1. the keysdisposedflush With the outer end of the core 1 8.A Thisl tubular sleeve portion. 42 slidably fits Within theA enlarged. Way. portion 23 with the inner end'of the'sleev-.e abutting'against theshoulder 44 formedl by7 providing the enlar-gedvvay portion 23. The

outer endo'f the sleeve portion 42,.aiitlwvliich\ projectsgpast the outer. endof thev keys 43, is

externally threaded as at 45 `for threadedre-- ception ofthe head-,35Ey Asvvill be observed,

` the bore ,'36, adjacent its open end, .is enlarged andathreaded `as,-azt4 ,for threadedreception of thethreadedf sleeve portion, 45 beiobserwed in' Figure:2,v the-internalzdiameter offthesleeve portion-42fis of a diameter to slidably receivein"A snugjfitting engagement,- the stem portion 31 of the electrode 30. This, plug y411,'andvvliich' may be. formed otanyvsuitab'l'efmetal,'serves as means for detachably connecting the .centralf. electrode.-

30 at its outer end, to the outer end of the core 18.

Carried by the outer end of the core 18, is a retaining cap 48 embodying a ring portion 49 engaging the side oi the core, and a iiat disc or plate portion 50 which is adapted to engage the flat end face 51 of the core and rest upon the outer ends of the keys 43 for retaining the plug 41 Within the outer end of the bore or Way 20. The inner edge of the ring portion 49 is crimped or curled into the annular groove 25 as in Figure 2, and this crimping or curling of the inner end of the ring serves to retain the cap 48 in position upon the 'outer end of the core 18. As Will be observed in Figure 2,l the threaded extension 45 of the sleeve portion 42 projects through the plate 50, and this plate is preferably adapted for threaded connection with the extension. 45.

Disposed about the threaded sleeve extension 45, between the cap plate 50 and the head 35,'is a yieldable gasket or Washer 55, and this Washer may consist of a copper shell provided with a packing such as asbestos or any other suitable material which may be readily compressed upon tightening of the central electrode 30.. This` compressible Washer 55 has been. provided in order that the shoulder '33 of the electrode `30 may be moved into sealing. engagement Withl the core 22 When the electrode 30l is properlygposi.- tioned Within the core 18. The slot 40 pro-l vided in the head 35v will permit. of the head being rotated by a1 screw driver WhenA positioning and removing: the electrode 30.` Y

When desiring to, remove the central' elec-` trode 30 in order that the iiringy point 32 of the electrode may be cleaned. so that a proper spark willv be produced. between the. point andthe electrode. 13 it merely necessary. to. rotatethe head 35- untilf the headbecomes. disconnected. from: the *threaded sleeve extension 45,.,and1after WhichT the stem of they electrodemay be readily Withdrawn itrom the Way 20 Without. requiring. the re-- moval of the shell` 1() from yits connection with. the engine. During removal and replacingK of the centralv electrode` 30, the keys' 43 ofthe plug 41,.,W-ill preventthe plugifrom. rotating inr either direction and the cap =48 Will' serve for retaining, the plug Hin-'proper position at the. outer end. of the. corel 18. After. removal*` of: ther central electrode, the firing point. 32 may lie-'scraped` for. removing. the carbonzdeposit thereirom,or may be heldv over aflame ina mannery as illustrated in Figure 6 for burning of the carbon deposit i'romthe liningpointof theelectrode. This heatingot thev stem portion. of.' the central electrode not' only. serves to. remove the carbon depositfromzthefiring, portion 32, but` also heats the electrodein .amanner Wherebyf when the electrode is again :positionedwithin thecore 1 8,v the .heat radiated from. the .stemt will serve to vaporize a portion of the explosive charge at the inner end of the spark plug and result in ready and easy starting of the engine, particularly in cold weather. It will further be seen that upon removal of the central electrode 30, that an opening is Jformed through the core 18. whereby gasoline or the like may be introduced through the way for priming of the engine.

From the foregoing description it will be apparent that a novel and practical type of spark plug has been provided which is of extremely simple construction, and which plug embodies a central electrode which is readily detachably connected at its outer end to the outer end of the plug, and which central electrode by means of its detachable connection with the body portion of the plug, will permit of the ready cleaning of the electrode without removal of the plug from the engine block, will permit of the electrode being heated for aiding in starting of the engine, and which electrode when removed allows for an opening to be formed through the plug whereby fuel may be introduced into the engine through the plug for priming of the engine.

Changes in detail may be made to the specific form of the invention herein shown and described, without departing from the spirit of the invention or the scope of the following claims.

I claim:

l. A spark plug, an insulating core having an axial way therethru and elongated keyways extending longitudinally of and opening into the way at the outer end of the core, a stem removably extending thru the way, and retaining means for the stem comprising a plug embodying elongated keys slidably itting in said keyways with the outer ends of the keys flush with the outer end of the core and an externally threaded extension projecting past the outer ends of the keys, a retaining cap embodying a plate portion in overlying engagement with the outer ends of the keys and a ring portion for crimped engagement circumferentially of the core, and a terminal head carried by the outer end of said stem for threaded connection with the threaded extension of said plug.

2. A spark plug, an insulating core having an axial way therethru provided intermediate its ends with an outwardly facing annular seat, a stem providing a central electrode, slidably and rotatably fitting in said way and having a reduced inner end portion providing an annular shoulder envageable with said seat, and retaining means or sealing the stem in said way comprising a plug ixedly mounted in the outer end of said core and having an externally threaded tubular extension aligning with said way, a terminal head carried by the outer end of the stem and having a bore for threaded connec- EARL J. JOHNSON. 

